1. Field of the Invention
The present invention relates to a magnetic recording method of writing data signals with a heat-assisted magnetic recording using an eddy current and thin-film magnetic head for the heat-assisted magnetic recording using the eddy current, a head gimbal assembly (HGA) with the thin-film magnetic head, and a magnetic recording/reproducing apparatus with the HGA.
2. Description of the Related Art
With the increasing capacity and decreasing size of a magnetic recording/reproducing apparatus such as a magnetic disk drive, further improvements of performance are required for the thin-film magnetic head. As the thin-film magnetic head, a composite-type thin-film magnetic head is widely used, which has a stacked structure of a magnetoresistive (MR) effect element for reading data signals from a magnetic recording medium such as a magnetic disk and an electromagnetic coil element for writing data signals, and the reading and the writing data signals are performed with using these elements to a magnetic recording media such as the magnetic disk.
Generally, the magnetic recording medium has a magnetically discontinuous layer where magnetic microparticles are gathered together. Usually, each of the magnetic microparticles has a single magnetic-domain structure, and one recording bit consists of a plurality of the magnetic microparticles. Therefore, for improving the recording density, irregularity in the boundary of the recording bit is required to be reduced by decreasing the size (volume) of the magnetic microparticle. However, a problem is likely to occur that decrease of the size of the magnetic microparticle causes thermal stability of the magnetization to be degraded.
As a measure of the thermal stability problem, it may be possible that the KU, which is a magnetic anisotropy energy in the microparticle, is increased concurrently. However, the increase in the KU causes the increase in coercive force of the magnetic recording medium. On the other hand, the write magnetic field intensity of the magnetic head is limited by the amount of the saturation magnetic flux density of the soft-magnetic material which constitutes a magnetic pole in the head. Therefore, the head cannot write data signals to the medium when the coercive force of the magnetic recording medium exceeds a permitted value which determined with the limit of the write magnetic field intensity.
As a further measure of this, a heat-assisted magnetic recording technique is proposed, in which the magnetic head writes data signals to the magnetic recording medium formed of a material with the large KU value, by reducing the coercive force of the medium with heat supplied to the medium just before the write field is applied.
At present, as a heating method of the magnetic recording medium in the a heat-assisted magnetic recording technique, a method of emitting a near-field light generated by a laser to the magnetic recording medium is mainly proposed. For example, Japanese patent publication No. 2001-255254A describes a near-field light probe which has a metal scatterer with strobilus shape formed on a substrate and a dielectric material film formed around the metal scatterer. And U.S. Pat. No. 7,133,230 describes a scatterer as a near-field light probe, which is formed in contact with the main magnetic pole of a head for a perpendicular magnetic recording in such a way that the irradiated surface of the scatterer is perpendicular to the surface of the medium. As means for providing this laser, U.S. Pat. No. 7,133,230 uses a semiconductor laser element equipped in the heads. And, for example, a technique described in Japanese patent publication No. 2000-173093A uses an optical fiber for provision of the laser.
Meanwhile, as a other method of heating the magnetic recording medium in the a heat-assisted magnetic recording technique, for example, US patent Publication No. 2004-252591A describes a technique which indirectly heats the magnetic recording medium using a heating element to heat a inductive write head layer. And, Japanese patent publication No. 2004-253043A describes a technique which heats the magnetic recording layer of the magnetic disk with heating a spacer by applying current between two yokes at the head which has two yokes and a spacer filling in a magnetic gap between two magnetic poles located in the each tip of its yoke.
However, a lot of technical difficulties occur and there is a problem in the heat-assisted magnetic recording technique using the laser or the heat from the heating element.
Certainly, in the heat-assisted magnetic recording technique using the laser, a suitable heat-assisted is enabled with efficiently and locally heating the magnetic recording medium. However, in order to realize the thin-film magnetic head for the heat-assisted magnetic recording, generally, it is necessary to form a microscopic optical system part which requires high position accuracy and dimension accuracy, which become a great task in manufacture process. And in a configuration of the typical thin-film magnetic head that the element-formed surface and the opposed-to-medium surface are perpendicular to each other, it is the great difficulty in a design to set a laser source so as to get light paralleled to the element-formed surface.
Also, in the heat-assisted magnetic recording technique using heat from the heating element, as the magnetic recording medium is heated with simple heat conduction, it is difficult to heat a predetermined position of the magnetic recording medium to sufficient temperature within a predetermined time. Furthermore, the problem that a thermal pole tip protrusion (TPTP) occurs and an air bearing surface (ABS) is changed by out of control has happened.